1. Field of the Invention
This invention relates to diphenylether-formaldehyde copolymer resins and their preparation. In one aspect, this invention relates to carboxylated diphenylether-formaldehyde copolymer resins wherein the copolymer has an average value of 0.1 to 1 for the number of carboxyl groups per repeating unit and there is an average of at least one carboxyl group per polymer.
The term "diphenylether" as used herein includes the corresponding thioether.
2. Description of the Prior Art
Resins prepared from the reaction of diphenylether and formaldehyde are not new. Makromol. Chem., 97, 163-73 (1966). Hydroxymethylated diphenylether-formaldehyde copolymers are also known. Masuko (JAP No. 46-34112). However, the art is deficient of a carboxylated diphenylether-formaldehyde copolymer resin, a process for its preparation, or a stable aqueous solution made therefrom.